How To Change Your Office 365 Account Picture

Sign into Outlook on the web at https://outlook.office.com
At the top of the page, select your profile picture (1) and then click on the existing photo or your initials (2).
You will then receive a popup that allows you to change your photo.
Select Upload a new photo.
Select Browse and choose the picture you want to use.
Drag or resize the image box, and select Save.